Patent GB-923846-A (GB)
Title: Surface treatment of films and other polymeric shaped structures
IPC: C08L27/00
Filed: 1961-06-15
Abstract: A process for modifying the surface characteristics of polymeric shaped structures such as films comprises subjecting the surface of such a structure to the action of an electrical discharge having an energy level below 15 electron volts in a gaseous atmosphere containing as an essential ingredient the vapour of an inorganic element or compound having an affinity for electrons and having a vapour pressure of at least 1 mm. of mercury at 60 DEG C.  The element or compound is preferably mixed with an inert carrier gas, such as nitrogen or carbon dioxide.  In the preferred embodiment of the invention, a continuous web of preformed self-supporting organic polymer film, e.g. of polyvinyl fluoride or of a copolymer of tetrafluoroethylene and hexafluoropropene is passed continuously between a set of spaced electrodes consisting of an earthed rotating metal roll and one or more stationary hollow metal tubes disposed parallel to the longitudinal axis of the roll and preferably spaced about 0,01 to about 0,0125 inch from the surface thereof.  The tubes are each connected electrically to a source of an alternating (or pulsating direct) current of the required intensity at a voltage preferably over 2000 to 3000 volts and at a frequency preferably of 300,000 to 500,000 cycles per second.  A mixture of the vapour of the element or compound and an inert carrier gas is fed continuously to the hollow interior of the electrode tubes at a rate of one half to 10 cu. ft. per minute and issues from them through openings at the gap between each tube and the roll. Current to the electrodes preferably ranges from 0,05 to 2,1 RF amperes and power to the electrodes may range from 10 to 100 watts per lineal inch of electrode length.  The time of exposure of the film surface to the electric discharge treatment should be at least 4x10-4 second.  The inorganic compound used may be boron trifluoride, aluminium trichloride or tribromide, silicon or titanium tetrachloride, hydrogen chloride, chromyl chloride, hypochlorous, perchloric, nitric or fuming sulphuric acid, chlorine dioxide, sulphur dioxide, sulphur trioxide, nitric oxide, nitrous oxide, nitrogen oxychloride, nitroxyl chloride, hydrogen sulphide, or ferric nitrate.  The inorganic element used may be chlorine, bromine or fluorine.  Specified polymeric materials are the polymers of perfluorocarbons, vinyl fluoride, chloride or acetate, vinylidene fluoride or chloride, ethylene, propylene, butene-1, styrene, ethylene terephthalate, amides, acrylonitrile, acrylates, methacrylates, urethanes, organic carbonates, acetals, spiroacetals; regenerated cellulose, cellulose acetate and cellulose ethers; coumarone-indene resins, epoxy resins, phenol-aldehyde resins, urea-formaldehyde resins, melamine formaldehyde resins, isocyanate resins and protein plastics.  In an example, an oriented polyvinyl fluoride film treated according to the invention in an atmosphere of boron trifluoride is coated with a mixture of 10 parts Epon 828 and 3 parts Epon U and the coated surfaces pressed together for 10 minutes at 120 DEG C. and 75 p.s.i. to form a laminate.  Laminates are similarly formed using a tetrafluoroethylene/hexafluoropropene copolymer films.  A polyester film treated according to the invention in an atmosphere containing chlorine is heat sealed at 190 DEG C. and 20 p.s.i. to form a laminate, no adhesive being used.  A polypropylene film treated according to the invention in an atmosphere of chlorine is coated with a vinylidene chloride/acrylonitrile copolymer to form a laminate in which the coating shows excellent adhesion to the treated film.  A film of regenerated cellulose containing 15% of glycerol treated in an atmosphere of boron trifluoride is coated with polyethylene and excellent adhesion of the coating obtained. In other examples laminates are prepared using the Swift Co. X7071 adhesive. Specification 829,600 is referred to.